1. Field of Invention
The present invention generally relates to a novel disposable test tape cassette for measuring the concentration of analytes in a fluid sample, and more specifically, to a continuous band of sensor test tape capable of analyzing glucose in a small sample of whole blood. The invention also provides an analysis device capable of receiving, dispensing and analyzing the test tape cassette.
2. Background
Detection and measurement of an appropriate analyte(s) in a small sample of blood or other biological fluid samples, at home or near the patient has become commonplace in clinical medicine and is aiding in the diagnosing, monitoring and treatment of many diseases. One prominent example of this practice is the way diabetics are able to self-monitor and control their blood glucose to near normal levels at home or at work. This type of self-monitoring and good control significantly reduces the risk of developing serious complications related to diabetes as shown by landmark outcome studies.
Good control, among other steps to be taken by the patient, requires routine self-monitoring of blood glucose levels at several daily intervals. Beginning in the early 1970's, relatively easy-to-use self monitoring devices provided blood glucose measurements by diabetics, allowing better control of blood glucose levels by utilizing the test results to determine proper insulin dosage or other medications to be administered. Early models of such blood glucose monitoring (BGM) devices were based on photometric principles of glucose detection, whereas more recent devices are biosensor (e.g. electrochemical) based in their operation.
In both versions of the BGM devices, generally a disposable, one-time-use reagent test strip is used in conjunction with the analysis device. Such test strips are generally small, flat and rectangular with the two ends serving separate functions. All such strips have a front end to receive a small volume of capillary blood from a finger stick. In addition, the front end contains an appropriate reagent mixture that reacts chemically with the analyte present in the blood sample, in this case glucose, to generate an appropriate signal; either a color change or an electrochemical signal proportional to the amount of analyte present in the fluid sample. In the optical BGM devices, the end result of the chemical reaction is a color change detected and measured, whereas in the biosensor based BGM devices there is an electrochemical reaction taking place resulting in an electrical signal detected and measured. The other end of the test strip is to be inserted into the BGM device to position the test strip in the appropriate place within the device for optical measurement or in the case of biosensor based devices, to make electrical contact for the electrodes built into the strips with the electrical circuitry built into the analysis device to receive electrical signals.
With any of the existing BGM devices, the patient or the end user must unwrap or unzip the metallic foil containing the test strip, or alternatively in certain brands open the top of a tightly fitted container and retrieve a single test strip every time, then make certain that the strip is inserted properly with the correct side up and the correct end in the slot provided in the device. Following a measurement taken from a sample of blood, the test strip must be removed and discarded safely and properly along with the cover foil.
There are a number of inherent disadvantages to the existing strips.
1. The user must always carry an adequate number of test trips in a separate container from the analysis device.
2. Many of the existing test strips are wrapped individually within some kind of metallic foil. The opening and the unwrapping of most of these metallic wrappers for the retrieval of the individual test strip require considerable effort and force. This is especially difficult to perform for many younger patients who constitute a large portion of the Type I diabetics and also for some older or seriously ill patients.
3. Safe and clean retrieval and disposal of the test strip contaminated with blood at the completion of the test adds additional time and effort to the self monitoring process and represents a potential source of health hazard.
4. The manufacturing process for these test strips is elaborate and costly. In the case of the biosensor-based strips, the process requires additional steps and components for incorporating electrodes into the test strips, hence increasing overall cost.
In recent years as described in U.S. Pat. No. 5,854,074, there has been developed and put into practice for use by diabetics and others, a sensor pack disposed in a housing of a sensor dispensing instrument capable of handling a plurality of individual test strips used one at a time and discarded after each use. The cartridge holds a limited number of strips, therefore limiting the number of tests per cartridge to no more than ten, and again each blood covered strip must be disposed of after use, creating a potential bio-hazard.
In a separate development a long-test-film cassette for an automated biochemical analysis instrument capable of handling fluid samples and multiple tests for each fluid sample is described in U.S. Pat. No. 5,077,010. The analysis instrument is designed for use in a clinical laboratory for testing many fluid samples for multiplicity of tests and requires proper refrigeration of the unused portion of the test film and incubation of said test film once a fluid sample is delivered to the test film.
There remains a need in the art for an apparatus and for a more convenient and less costly method of self-monitoring of blood glucose. The method should yield a user-friendlier means of measuring blood glucose at home or at the workplace.